SUBJECT AREA: Physics

CONCEPTS: Centripetal forces, centrifugation, potential and kinetic energy.

MATERIALS:

A bucket

Some string

Water

PROCEDURE:

Simply fix the string to the bucket so that you can hold the bucket at the end of the string and so that you can fill the bucket up about half way with water. When you have filled up the bucket with the desired amount of water. Swing the bucket back and forth some, until you are ready to try and swing it around so that the bucket is upside down during each revolution. Imagine that you are a cowboy trying to rope a stray cow with a lasso. It works best to keep the string and bucket swinging at a 90 degree angle to the floor.

QUESTIONS:

1. Why did the water not fall/stay in the bucket?

2. Does it matter how fast I spin the bucket?

3. Does it matter how long the string is?

4. Does it matter how much water is in the bucket?

5. Does the bucket overcome the force of gravity?

RATIONALE:

This is a simple demonstration of centripetal force. The water, when it is set in circular motion, tends to want to move in a line tangent to that of its circular pathway. It pushes with a force outward into the bottom of the bucket. The bucket, however, acts an opposing force to the water, and holds it in place. If there were no bucket, the water would simple splash out in a line tangent to its starting point. Also, a certain velocity must be achieved, in order to overcome the force of gravity at the apex of the swing motion.